1. Field of the Invention
This invention concerns the removal of color-forming oxazole from acrylonitrile monomer as oxazole sulfate from which oxazole can be readily recovered.
2. Description of the Prior Art
According to the so-called ammoxidation process for making acrylonitrile, propylene is reacted with ammonia and oxygen in the presence of a catalyst at about 450.degree. C. There are several by-products of that reaction including oxazole. Oxazole, having the formula, ##STR1## is a known compound. It is useful in insecticides against fiber-eating insects; see U.S. Pat. No. 3,359,158.
Oxazole has been characterized as a color-forming agent in the presence of acrylonitrile monomer. See, for example, U.S. Pat. No. 3,524,875, U.S. Pat. No. 3,686,263 and British Pat. No. 1,180,556.
Oxazole is removed from acrylonitrile according to U.S. Pat. No. 3,524,875 by a process of fractional distillation; according to U.S. Pat. No. 3,686,263 by complexing it with certain metal salts; according to British Pat. No. 1,180,556 by passing the oxazole-containing acrylonitrile through an ion exchange resin; and according to U.S. Pat. No. 3,697,576 by contacting it with an adsorbent (e.g., alumina, clay) for the oxazole.
According to the method of U.S. Pat. No. 2,555,798, acrylonitrile and a nonvolatile polybasic inorganic acid are treated by a steam distillation process. Certain unrelated salts of oxazole, including the picrate and the hydrochloride, are referred to in Cornforth et al. J. Chem. Soc. 96 (1947), pages 96 to 102. General background on oxazole is contained in Wiley, Chem. Rev. 37, (1945), pages 401 to 442. The Wiley article is concerned solely with substituted oxazoles.